Pain, in and of itself, constitutes a sufficient impetus for remedial action. Moreover, otherwise productive individuals lose more time due to pains, particularly in the joints, than to any other cause. Civilization and technological advances have ushered in a relatively sedentary existence, both as to work environment and leisure activities, which increases the likelihood of such pain-causing ailments. Although the term is applied to a wide variety of disorders, arthritis generally denotes the inflammation of a joint whether as a result of a disease, an infection, a genetic defect or some other cause. The long term effects of arthritis range from chronic pain to crippling disability.
Osteoarthritis is a disease that attacks cartilage. Surfaces of joint cartilage and underlying bone compress and become irregular, leading to pain, inflammation, bone spurs and limited movement. Osteoarthritis is one of the most common disabilities in the United States, affecting over 15% of the population. As osteoarthritis progresses, serious joint damage and chronic pain can result. Treatment alternatives are limited and, in many cases, ineffective. Aside from weight reduction and avoiding excessive stress on the joint cartilage, there is currently no specific treatment to halt cartilage degeneration or to repair damaged cartilage caused by osteoarthritis. The goal of treatment is to reduce joint pain and inflammation while improving and maintaining joint function. Current pharmacological treatments include oral anti-inflammatory and anti-pain medications. The effectiveness of these treatments decreases as the disease progresses. In severe osteoarthritis, joint replacement surgery is common. Sometimes surgery is forestalled with injections of steroids into the affected joint, but the delivery of drugs in this manner is painful, and the drugs themselves provide decreasing effectiveness and wear off after several weeks. In 1999, there were over 500,000 joint replacement surgeries funded by Medicare in the United States, which were likely mainly due to osteoarthritis.
Severe arthritis involves a serious auto-immune reaction for which steroids theoretically provide treatment. The efficacy of steroids, however, is compromised by the systemic toxicity resulting from the dosage required to penetrate the natural barriers of the joints and the need for repeated treatments due to the chronic nature of the disease.
Steroids can be administered in different ways. For example, they can be orally ingested as tablets, or by injected into a muscle or into a vein.
Steroid injections are a common treatment for a variety of conditions in which inflammation causes pain, swelling and other problems. Joint pain due to osteoarthritis and rheumatoid arthritis are examples of conditions for which steroid injections may be helpful. Injections have the advantage of placing the steroids, often glucocorticoids, for example, directly into a painful area. Because of this, steroid injections are able to reduce inflammation and pain relatively quickly. Unfortunately, steroid injections must be administered by a medical doctor, are sometimes accompanied by an anesthetic to numb the area to be injected, and typically last for only several months before a second injection is required. Furthermore, the injected area may become more painful over the first 24 hours after the local anaesthetic wears off, requiring application of a cold compress or painkillers. In addition, it is usually suggested that the joint be rested for 24-48 hours after the injection, especially for weight-bearing joints such as the knee. Immediately after injection, the concentration of steroid within the joint is maximal. The injection, however, becomes progressively less effective however as the steroid clears the joint. Repeated injections to maintain therapeutic drug concentrations are not clinically acceptable, yet high initial doses carry a risk of toxicity. It is difficult to maintain therapeutic drug concentrations.
Common side effects associated with steroid treatment include weight gain, thinning of the bones (osteoporosis), easy bruising, indigestion, mood changes, rises in blood sugar and blood pressure, and increased likelihood of developing infections. Because of their long-term side effects, it is recommended that corticosterolds should be given only after a careful and usually prolonged trial of less hazardous drugs. Furthermore, severe rebound follows the withdrawal of corticosterolds in active diseases, in part due to the down regulation of naturally occurring glucocorticoid steroids.
Intraarticular injections of corticosteroids may temporarily help control local synovitis in one or two particularly painful joints. Triamcinolone hexacetonide may suppress inflammation for the longest time; other depot corticosteroids, including prednisolone tertiary-butylacetate, also are effective. The soluble 21-phosphate preparations of prednisolone or dexamethasone are not recommended because of rapid clearance from the joint and very short duration of action. Side effects may not be as pronounced when steroids are given by injection to the knee. However, the effects of a steroid injection to the knee typically is limited to several months before another injection is required. Also, injections provide an initial level of steroid that is greater than therapeutically required and which rapidly declines beneath therapeutic levels.
Cytotoxic/immunosuppresive compounds (e.g., methotrexate, cyclosporine) are increasingly used for severe, active rheumatoid arthritis. They can suppress inflammation and may allow reduction of corticosteroid doses. Yet, major side effects can occur, including liver disease, pneumonitis, and bone marrow suppression. Thus, patients require careful supervision by a specialist.
Broadly, there exists a need for an improved implantable sustained release drug delivery device and method and apparatus for implantation of said device. In particular, there exists a need for an improved device and method for treating conditions of joint or bones, such as arthritis, without undesirable systemic side effects and a need for repeated injections.